Anaotmical variability in the position of cystic artery and its affect on surgical approach during laparoscopic cholecystectomy

Background: The laparoscopic view of extrahepatic biliary tract and cystic artery is different anatomically from open approach. Consequently iatrogenic injuries due to inadverent damage to cystic artery are not uncommon. These complications can be prevented by careful dissection in Calots triangle and better knowledge of laparoscopic anatomy of cystic artery and its variations. The aim of this study is to establish the prevalence of variation in position of cystic artery in relation to cystic duct in Asia’s largest slum area. This will help identify the safe area for dissecting peritoneum in Calots triangle and thus help young surgeons overcome the long learning curve associated with laparoscopy. Methods: During a 2 year period from 2018-2019, 192 laparoscopic cholecystectomies that were performed at a tertiary care hospital were studied. Patients above the age of 70 years, pregnant females, patients with history of previous abdominal surgery and the cases of conversion from laparoscopic to open cholecystectomy were excluded from the study. Cystic artery was divided into four groups based on its relative position to cystic duct. It includes superomedial, superolateral, anterior and absent cystic artery relative to the cystic duct. Results: Out of 192 cases of laparoscopic cholecystectomy 174 (90.62%) patients had cystic artery superomedial to cystic duct and 10 (5.208%) had a cystic artery at superolateral position to cystic duct. In 5 (2.6%) patients it was found anterior to cystic duct and in 3 (1.56%) patients it was absent. Conclusions: As the least common position of cystic artery was found to be anterior to cystic duct in our study, it is concluded that blind dissection from anterior side is the safest approach to avoid injury to cystic artery. This technique can help young surgeons overcome the long learning curve associated with laparoscopy.

study, it is concluded that blind dissection from anterior side is the safest approach to avoid injury to cystic artery. This technique can help young surgeons overcome the long learning curve associated with laparoscopy.

Background
Cholelithiasis is one of the most common and prevalent surgical pathology all over the world 1,2,3 . The laparoscopic view of extrahepatic biliary tract and cystic artery is different anatomically from view in open approach. The introduction of laparoscopic technique has revolutionized the management of cholelithiasis. Although it has a very long learning curve, yet it is now the standard procedure for symptomatic cholelithiasis 4 as it offers signi cant bene ts over open technique. 5 Despite its advantages laparoscopic cholecystectomy was initially associated with a higher number of iatrogenic bile duct injuries and arterial haemorrhages 6,7 . This was due to the fact that a surgeon who is J.F. Calot in 1891 described a triangular area comprised of the cystic duct, right hepatic duct, and lower edge of the liver. 8 Rocko et al in 1981 described the possible variations in the region of Calot's triangle 9 In 1992, Hugh et al suggested Calot's triangle should be renamed the hepatobiliary triangle, with the small cystic artery branches supplying the cystic duct being called Calot's arteries 10 The cystic artery typically arises from the right hepatic artery and courses within the cystohepatic triangle to the right of the common hepatic duct. 11 Bleeding of cystic artery is a very troublesome complication during laparoscopic cholecystectomy as it decreases the overall visibility in abdomen. Reported incidence of conversion to open surgery because of blood vessel injuries is approximately 6.62%. 12  The present study is conducted to nd the prevalence of positional variations in cystic artery as seen in laparoscopic view in a local population of the largest slum area in Asia. The aim of this study is to identify the variation in position of cystic artery in relation to cystic duct so that we can identify the safe area for dissecting peritoneum in Calots triangle. This study can play its part in decreasing the incidence of vascular complications in laparoscopic cholecystectomy and help young surgeons with minimal experience overcome the long learning curve associated with it.

Methods
This is a prospective, sequential, non-randomised, descriptive study which was conducted at a tertiary care hospital within duration of two years from 2018 to 2019. All the patients who were admitted with the diagnosis of cholelithiasis and underwent elective laparoscopic cholecystectomy were included in this study during the speci ed duration.
All patients who were converted to open cholecystectomy were excluded from the study. Patients above the age of 70, pregnant patients and patients with the history of previous upper abdominal surgeries were also excluded from this study.
Sample size was calculated using WHO sample size calculator with one-sided hypothesis test mode. The level of signi cance was 5% while the power of the test was set to be 95%. Non probability consecutive sampling technique was used thus nullifying the selection bias. The sample size was calculated to be 192.
After approval from ethical committee, informed consent was taken from patients. All patients underwent routine investigations and ultrasound of whole abdomen prior to surgery. Complete blood count, liver function test were done to rule out acute cholecystitis. Three surgeons performed the surgeries in a randomized fashion. All surgeries were carried out under general anaesthesia. Pneumoperitoneum was created by Veress needle. A standard 4 port approach was used to proceed with cholecystectomy. Olympus laparoscope with 0 degree camera was used. Visualisation of Calots triangle and variations in position of cystic arteries were visualized on medical grade monitor and duly noted in the prescribed performa. Variations in the position of cystic artery were classi ed into 4 groups as shown in Table 1. Table 1 Anatomical groups of cystic artery in relation to cystic duct.

Group
Cystic artery position Prevalence The study revealed that among these 192 patients 174 (90.62%) had cystic artery at superomedial position to cystic duct and were included in group 1 ( Figure A). The second most common position was found to be cystic artery posterolateral to cystic duct in 10 (5.208%) patients and included in group 2 ( Figure B). In 5 (2.6%) patients cystic artery was found to be at anterior position to cystic duct ( Figure C) and absent in 3 (1.56%) patients thus included in group 3 and 4 respectively.

Discussion
The course, length and position of cystic artery are highly variable and are thus prone to iatrogenic injury. In order to avoid such complication it is essential to perform careful blunt dissection in Calots triangle during laparoscopic and open cholecystectomy. In this study we aim to establish a safe approach zone for dissection in Calots triangle. We studied the variations in cystic artery anatomy with relation to the cystic duct aimed to determine an area of dissection least likely to encounter cystic artery. We found that the superomedial was the most common position (90.62%) in relation to cystic duct and the least common position was found to be anterior (2.6%). It was found absent in 3 (1.56%) patients. It has previously been described in literature that in cases where cystic artery cannot be found in the Calot's triangle, the gall bladder receives its blood supply from vessels arising directly from the liver parenchyma. 14 In view of these results we aim to establish that it is safe to dissect the peritoneum anterior to the cystic duct as this is the area with least prevalence of cystic artery. The thorough knowledge of anatomy of extrahepatic biliary tract arterial supply and its variation is crucial. This knowledge helps in reducing the unwanted bleeding that might result in obscuring the vision causing damage to other biliary and vascular structures. Iatrogenic injury to common bile duct and cystic artery can be avoided by careful dissection at Calots triangle and hepatoduodenal ligament 18 It is thus essential to establish a safe zone for the blind dissection where the cystic artery can be present least likely. This study provides evidence for this step to be carried out safely without bleeding the cystic artery. As a rst step in achieving critical view of safety, blind dissection in Calots triangle can be safely started anterior to the cystic duct thus reducing the chance of injury to cystic artery.

Conclusion
It is concluded in this study that during laparoscopic cholecystectomy the blind dissection in Calots triangle, as the rst step to achieve critical view of safety, should be performed anterior to the cystic duct. It is least likely to encounter cystic artery while proceeding with this approach thus reducing the complication of iatrogenic injury. Young surgeons can bene t from these ndings in overcoming fear of complications and the learning curve associated with laparoscopic approach.

Declarations
Ethics approval and consent to participate Ethical approval was taken from the Institutional Review Board of Sindh Government Qatar hospital where the study was conducted. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (name of institute/committee) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Syed Muhammad Abdullah Bukhari: Writing of manuscript, Data collection.  Anterior position of cystic artery